Taxonomy & naming
Sternarchella raptor was described by Lundberg, Cox Fernandes & Albert in 1996 and placed in the family Apteronotidae, the ghost knifefishes, within the order Gymnotiformes — the New-World electric knifefishes. Like every gymnotiform it is a bony fish, but an unusual one: the order is defined by an electric organ and a long ribbon-like anal fin rather than by the fin arrangement typical of most freshwater fish, and it produces a weak electric organ discharge (EOD) used both to sense its surroundings (electrolocation) and to signal other knifefish. In the Apteronotidae that organ is built from modified nerve cells rather than muscle, giving the family the fastest, most refined wave-type discharges in the order.
A taxonomic revision published in the journal Neotropical Ichthyology (Lundberg et al., 2018) confirmed that the genus Magosternarchus raptor, once treated separately, is a junior synonym of Sternarchella raptor, folding the two names together and placing this species within the S. duccis species clade. The type locality lies in the río Solimões, Amazonas, Brazil, roughly 11 mi downriver from its confluence with the río Purus. As with all valid names on this site, the Catalog of Fishes (Eschmeyer, CAS) is treated as the authority. The common name 'knifefish' is shared with the unrelated Asian featherback and clown knifefishes (Chitala, Notopterus), which belong to an entirely different order and are not kin to this species.
Morphology
Sternarchella raptor is the largest known species in its genus, reaching about 16 in in total length — a substantial, deep-channel Amazonian knifefish. It shares the family's blade-like body plan: laterally compressed, tapering to a slender tail, propelled by a single very long anal fin thrown into travelling waves rather than by a tail fin, with no dorsal fin. It is entirely scaleless, its skin smooth and directly exposed to the surrounding water.
The feature that distinguishes it, and gives it its common name, is its jaw armament: a large, broad anterior maxilla process and well-developed gill rakers support enlarged jaws and robust oral and pharyngeal dentition, far heavier than the fine teeth of most ghost knifefish. This dentition is built for a specialised, facultatively lepidophagous diet — biting external body parts, including fins and flesh, from other electric knifefishes rather than swallowing prey whole. Running along the body is the electric organ, generating a wave-type discharge, with sensory pores across the skin reading the field it produces; this electrosense is the fish's primary means of finding its way and its targets in the dark, deep water it inhabits.
Habitat
This species lives in the deep channels of the Amazon River and its larger tributaries, at depths from roughly 2 to 50 metres, within the Solimões basin of Amazonas, Brazil. It is a fish of the main river bed rather than of marginal vegetation or floodplain shallows — cool, dark, fast-flowing water far below the turbid surface, where sunlight is negligible and life is organised around senses other than sight.
In that environment electrolocation is not a supplementary sense but the primary one: a nocturnal, deep-water existence with essentially no light makes a self-generated electric field the most reliable way to detect structure, prey and other fish. Specific water chemistry data for this species have not been documented in the sources available; it can be inferred to share the warm, soft, Amazon-basin conditions typical of its relatives, but that should be treated as an inference rather than a measured record for S. raptor itself.
Feeding
Sternarchella raptor is a specialised predator with a diet unusual even among the electric knifefishes: it is facultatively lepidophagous, meaning it feeds by biting external body parts — fins and patches of flesh — from other Gymnotiformes sharing its deep-channel habitat, rather than relying solely on whole invertebrate prey. Its enlarged jaws, broad maxilla process and heavy dentition are the physical toolkit for this habit, and its well-developed gill rakers point to a diet that also includes more conventional invertebrate prey taken from the water column or substrate.
As in other Apteronotidae, targets are located primarily through electrolocation rather than vision, an approach that works as well in the near-total darkness of a deep river channel as it does at night nearer the surface. Because the species is essentially unknown in captivity, there is no aquarium feeding record to draw on; its known diet is inferred from jaw morphology and field observation rather than from observed feeding trials.
Mating
No species-specific courtship behaviour has been documented for Sternarchella raptor. What can be said follows from its family: in Apteronotidae the wave-type electric organ discharge carries information about a fish's identity, sex and reproductive state, and courtship in well-studied relatives involves mutual shifts in discharge frequency — an electric exchange running alongside physical approach in the dark. It is reasonable to expect a broadly similar signalling role for S. raptor's own EOD, but this has not been directly studied or reported for the species, and the point should be read as inference from the family rather than an observed fact.
Breeding
Sternarchella raptor is presumed to be an egg-layer, consistent with the rest of the Apteronotidae, but no breeding has been documented in the wild or in captivity, and the species is not established in the aquarium trade. As with most deep-channel gymnotiforms, no parental care has been recorded. Data on spawning site, egg number, incubation or any other detail of reproduction are simply not available for this species — it should be treated as data sparse rather than filled in by analogy to better-known relatives such as the black ghost knifefish.
In the aquarium
Sternarchella raptor is not an aquarium fish in any practical sense: it is a deep-channel Amazonian species with no established presence in the trade, and there are no husbandry records to draw on. Were it ever to be kept, the same baseline cautions that apply across the ghost knifefishes would hold — it is scaleless and would be expected to be sensitive to ammonia, nitrate and copper-based medications, and as a specialised nocturnal predator with jaws built for attacking other knifefish, it would be entirely unsuitable to house with other electric fish, let alone smaller tankmates. This entry exists for completeness of the genus rather than as a stocking recommendation; anyone encountering the species should treat it as a scientific specimen, not a community or even a specialist single-species aquarium fish.
Conservation
Sternarchella raptor is assessed on the IUCN Red List as Least Concern, notwithstanding the general pattern for deep-channel Amazonian gymnotiforms that are rarely encountered, poorly studied in the wild and absent from the aquarium trade. Its known range within the Solimões basin lies within the broader Amazon system, which faces basin-wide pressures from deforestation, damming and mercury contamination linked to mining, but no evidence ties a specific threat to this species, and its habitat — the deep main channel of a very large river — offers some inherent buffering against local disturbance.